Strip breakage detecting apparatus for continuous strip furnaces



Sept. 13, 1960 w. s. GIBBS STRIP BREAKAGE DETECTING APPARATUS FOR CONTINUOUS STRIP FURNACES Fil ed Oct. 22, 1958 INVENTOR WILL/AM 6. GIBBS 25 By M1.

2,952,451 Patented Sept. 13, 1960 sTRlP BREAKAGE DETECTING APPARATUS FOR CONTINUOUS STRIP FURNACES William G. Gibbs, Mount Lebanon Township, Allegheny County, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed Oct. 22, 1958, Ser. No. 768,977

6 Claims. (Cl. 263-3) This invention relates to vertical heat treating towers or furnaces of the type used in lines for continuously processing metal strip and, more particularly, to an apparatus for detecting and locating strip breakages in a furnace or tower and for stopping the travel of metal strip therethrough in response to a strip breakage.

When strip breaks in a-continuous annealing or other heat treating furnace, it is necessary to stop the conveyor rolls which deliver the strip through the furnace in forwardly through the furnace, and to prevent a pile-up or accumulation of strip in the space between the furnace bottom and the lower conveyor roll immediately in advance of the point of breakage, which may cause another break in the strip after welding if it is sufficient to jam such space and prevent movement of the strip therethrough upon subsequent operation of the conveyor rolls. Delay in stopping the furnace conveyor rolls further results in pulling a section of the strip out of engagement therewith and the necessity of rethreading the strip through several vertical passes before a repair weld may be made. Prompt stoppage of the furnace conveyor rolls in response to strip. breakage is thus required both to prevent furnace damage and to reduce the time required for strip repair cluring which the processing line is out of operation.

In conventional strip heat treating furnaces, strip breaks in a furnace can be detected only by observing the action of the strip outside of the furnace. By reason of the time that elapses between a strip breakage and a noticeable change in the action of the strip outside of the furnace, stoppage of the furnace conveyor rolls is subject to delay that varies according to theability of diiferent operators. Moreover, detection of a strip break by the resulting action of the strip outside of the furnace is extremely 'difiicult in the case of some metals such as,

for example, silicon strip which must be operated. with a rmnirnum amount of strip tension at annealing temperatures because of its mechanical properties. After stoppage of the furnace conveyor rolls, the point of strip breakage in the furnace must be located before the required strip welding operation can be performed. In conventional furnaces, the location of the point of strip breakage can be determined only by removing individual bungs or explosion plugs from the top and bottom of the furnace, or covers for access openings in the sides thereof, to expose the strip passes within the furnace. Since several openings may have to be uncovered in order to locate the point of strip breakage in this manner, further delay is introduced from the standpoint of restarting the t furnace operation.

Thisinvention accordingly has as one of its principal in operation after a breakage of the strip takes place therein. Another and related object is to provide an apparatus which will both detect and determine the location of strip breakage inthe furnace, and which will operate in response thereto to stop the operation of the conveyorrolls used to deliver the strip therethrough.

A further object of the invention is to provide a strip breakage detecting apparatus for continuous strip furnaces of the character mentioned above which comprises a plurality of electric circuit means that respectively and continuously observe the continuity of the strip extending between each pair of upper and lower conveyor rolls, and include the strip as part of its operating circuit. In conjunction therewith, the invention further contemplates the provision of relays which are actuated in response to the opening of any such operating circuits as the result of a stripbreakage to indicate the point of strip breakage and to stop the operation of the furnace conveyor rolls.

Other objects and advantages of the invention will be come apparent from the following description.

In the drawings, there is shown a preferred embodiment of the invention. In this showing:

Figure 1 is a schematic view illustrating a strip breakage detecting apparatus constructed in accordance with the principles of this invention and showing diagrammatically its application to a vertical continuous strip furnace or tower; and

Figure 2 is a side elevational view of a bearing support for one of the upper conveyor rolls of the apparatus shown in Figure l in which parts thereof have been broken away and shown in vertical section.

Figure 1 shows the usual arrangement of upper rolls 1 and lower rolls 2, of a roller conveyor in. a vertical heat treating furnace 3, and the manner in which metal strip S is threaded over such rolls for continuous movement through successive vertical passes in the furnace. In furnaces of this type, the conveyor rolls are driven by separate motors or by motors respectively arranged for driving a group of such rolls. Since the drive for rotating the rolls 1 and 2 is conventional, it has been shown diagrammatically as comprising a pair of motors 4 and 5- respectively having driving connections indicated by the broken lines 6 with the upper rolls 1 and lower rolls 2. In accordance with the principles of this invention, operation of the motors 4 and 5, and thereby movement of the strip through the furnace by rotation of the rolls 1 and 2, is controlled by a motor relay 7 and a plurality of strip relays 8, there being a separate strip relay 8 associated with each of the upper rolls 1. In a manner to be described, the relays 8 control the operation of the motor relay 7 and operate it to open the energizing circuit for the motors 4 and 5 to stop the rotation of the rolls 1 and 2 and movement of the strip S thereby at any time a strip breakage takes place in the furnace 3. The strip relays 8 further operate in a manner to be described to indicate the location in the furnace 3 of the break in the strip S.

A voltage reducing transformer 9 provides for energization of the motor relay 7 and strip relays d. It includes a primary winding 10 that is connected across a source of alternating current as indicated, and a secondary winding 11 that energizes the operating coil 12 for the motor relay 7 and the operating coils 13 for the strip relays 8 when their respective circuits are completed to ground terminals 1 as shown in Figure 1. As further shown in Figure l, the grounding connection required to complete an energizing circuit for each strip relay coil 13 includes a conductor 15, a top roll 1, a portion 16 of the strip S extending between such top roll 1, and a lower roll 2. While the lower rolls 2 are diagrammatically shown connected to ground by conductor leads 17, it will be understoodthat the conventional mounting of the lower V 3 is provided with a relay of this character.

3 rolls 2 places them at ground potential and a separate connection for this purpose is not required.

To prevent grounding of the energizing circuits for the strip relay coils 13 at points intermediate the conductors 15 and the lower rolls 2, each of the upper rolls 1 must be electrically insulated with respect to ground potential. The manner in which the conventional support at each end of the upper rolls 1 is modified for t is purpose is shown in Figure 2. In this showing, the numeral 18 designates the journalat one end of the roll 1 which extends through an opening 19 in a side 20 of the furnace 3. It is rotatably supported in a conventional manner by a bearing assembly 21 and a bearing capQZ on a pedestal 23. For the purposes of this invention', a strip of insulating material an is inserted between the pedestal 23 and the frame 25 on which it is supported, and a strip of insulating material 26 is iiiserted between the bearing cap 22 and the bellows 27 that provides an air seal about the opening 19 through whichthe journal 18 extends. The insulating strips 24 and 26 respectively operate to prevent grounding of the rolls 1 through the supporting frame 25 and the furnace sides 20. Electrical connection of the conductor 15 with the roll 1 is effected by a stationary carbon brush 28 which has sliding engagement with a conductor ring 29 keyed on the end of the journal 18 for rotation with the roll 1. To further prevent grounding of the roll 1 through its rotary drive, the drive therefor may conveniently comprise a chain and sprocket drive 30 between its drive motor 4 and the roll 1 which includes a sprocket 31, formed of fibre or other electrical insulating material, keyed on the end of the journal 18.

Each of the relays 8 has a normally closed contactor 32' and a normally open contactor 33. The contactors 32 of the plural relays 8 are arranged in series in the energizing circuit 34- for the motor relay coil 12. When the coil 12 is energized, a condition which is had only when all of the strip relay contactors 32 in its energizing circuit 34 are closed as shown in Figure 1, relay 7 picks up and operates contacts 35 to their closed position in which they connect both motors 4 and 5 to alternating current supply buses 36. g

An electric lamp 38 or other signal, is provided in conjunction with each relay 8 and operates to indicate its operating condition and thereby the continuity of the strip 16 between one of the upper rolls 1 and a lower roll 2. Operation of each indicator lamp 38 is effected by an energizing circuit 39 which is completed to ground upon movement of a normally open strip relay contactor 33 to closed position. When one of the relays 8 is deenergized and drops out in response to a strip breakage, its contactor 33 moves to closed position and operates a signal lamp 38 to indicate both that the strip S has broken and the location of its breakage in the furnace 3. The lamps 38 in practice are preferably located at a common control station where they furnish an indication to the operator of the relay 8 that has operated and thus the point of strip breakage in the furnace.

While Figure 1 shows strip relays 8 associated with only a few of the upper rolls 1 in a vertical strip furnace or annealing tower, it will be understood that each of the upper rolls 1 along the entire length of the furnace In operation, rotation of the rolls 1 and 2 by their drive motors 4 and 5 is prevented until the strip S has been threaded over all of the rolls 1 and 2 in the furnace to thereby complete energizing circuits for the operating coils 13 and the relays 8. When energizing circuits for all of the relay operating coils 13 are completed in this manner, the relays 8 operate to close the series contactors 32' and complete the energizing circuit 34 for the motor relay coil 13 with the secondary transformer winding 11 and the relay 7 picks up and closes the relay contactors 35 to connect the motors 4 and 5 to the alternating current supply buses 36. Operation of the motor relay 7 in this manner places the rotation of the rolls 1 and 2 under the control of the motor controllers (not shown) customarily provided in apparatus of this character.

During further operation of the furnace, breakage of the strip' S at any point within the furnace will open an energizing circuit 15 for one of the relays 8 by interrupting the portion thereof that is normally provided by one of the strip sections 16. When one of the relays 8 drops out in this manner, its contactor 32 moves to open position to interrupt the circuit 34 to the motor relay coil 12, and the motor relay 7 drops out to stop the motors 4 and 5 and thereby further rotation of the conveyor rolls 1 and 2. At the same time, its contactor 33 moves to closed position and operates a signal lamp 38 to indicate the point of strip breakage within the furnace 3. Since the apparatus of this invention operates promptly in response to strip breakage within the furnace to both stop the conveyor rolls and to indicate the point of strip breakage within the furnace 3, it will be apparent that the time required for replacing the furnace in operation is reduced compared to the time required for the repair of a strip break in conventional arrangements. Attention is particularly directed to the fact that the inclusion of a section 16 in the strip S as part of the energizing circuit for each relay 8 renders it elfective to continuously observe the continuity of the strip extending between each pair of upper and lower rolls, and thereby enables it to respond promptly to a breakage of the strip S in any of the sections 16.

While one embodiment of my invention has been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. In a continuous strip furnace having upper and lower sets of conveyor rolls over which strip moving therethrough is trained, the combination with said furnace and said rolls of means including insulating supports for electrically insulating each of said upper rolls with respect to ground potential, separate circuit means connected with each of said upper rolls and adapted to be closed through the strip trained thereover and one of said lower rolls, means including a relay operated by opening of any one of said circuit means in response to strip breakage, drive means for rotating said rolls, and means for stopping the rotation of said rolls by said drive means upon operation of said relay.

2. An apparatus as defined in claim 1 characterized by a separate signal means associated with each of said circuit means, and means responsive to opening of any one of said circuit means for operating the signal means associated therewith to indicate the location of strip breakage in said furnace.

3. Strip breakage detecting apparatus comprising, in combination, a continuous strip furnace having upper and lower sets of conveyor rolls over which the strip is trained, said upper and lower rolls being arranged in vertically spaced pairs respectively providing successive vertical passes over which the strip travels through said furnace, an electrically insulated support for one of the rolls in each of said pairs and an electrical ground-connection for the other of the rolls therein, separate circuit means connected with each of said one rolls and adapted to be electrically connected to ground through the said other roll in each of said pairs by the strip trained thereover, and separate indicator means associated with and operated by each of said circuit means upon opening 1 of its connection to ground in response to strip break- 5. Strip breakage detecting apparatus as defined in claim 4 characterized by said control means including a control relay and an energizing circuit therefor having a plurality of contactors connected in series therein, and by each of said circuit means including a relay for actuating one of said contactors to open said energizing circuit in response to strip breakage.

6. Strip breakage detecting apparatus comprising, in combination, a continuous strip furnace having upper and lower sets of conveyor rolls over which the strip is trained, said upper and lower rolls being arranged in vertically spaced pairs respectively providing successive vertical passes over which the strip travels through said furnace, insulating supports for electrically insulating each of said upper rolls with respect to ground potential, separate circuit means connected with each of said upper rolls and adapted to be closed through the strip trained thereover and one of said lower rolls, separate control relays operated respectively by opening of any one of said circuit means in response to strip breakage, each of said control relays having a pair of control contactors actuated thereby, and indicator means opera-ted by actuation of one of said control contactors for indicating the point of strip breakage in said furnace, drive means for rotating said rolls, a relay controlling the operation of said drive means, and an energizing circuit for said drive means relay in which the other of said pair of control contactors are connected in series, said other control contactors being normally closed whereby operation of any one of said circuit means in response to strip breakage operates to open said drive means relay energizing circuit to stop rotation of said rolls by said drive means.

References Cited in the file of this patent UNITED STATES PATENTS 

